Dual power telescope

ABSTRACT

A dual-power telescope is disclosed comprising objective means, an eyepiece, and a Galilean telescope adapted to be interposed therebetween with the Galilean ocular positioned between the objective means and its focal plane and the Galilean objective positioned between the eyepiece and the focal plane of the objective means.

United States Patent Inventors Robert E. Curtiss [56] References CitedCupertino: UNrrED STATES PATENTS Frank F. Rand, Jr., Los Altos Hills,Calif. 729 848 6/1903 Common 35o/194 Qllp No' 2193224 1969 936,54110/1909 Kenner 35o/42 P'f t d Mpr' 30 1971 1,042,346 10/1912 Hen1e.....350/38Ux a F" e a 1,290,777 1/1919 OBn'en 35o/20 Assgnee Lockheed ArF'aCorpo'am 2,409,186 10/1946 B6uwers.... 35o/20 Bmbmk Cam' 3,173,0123/1965 Dewinter 35o/20x Primary Examiner-David H. Rubin Attorneys-Robert B. Kennedy and George C. Sullivan DUAL POWER TELESCOPE l Claim 8Drawmg Figs' ABSTRACT: A dual-power telescope is disclosed comprisingU.S. Cl 350/20, objective means, an eyepiece, and a Galilean telescope350/212, 350/54 adapted to be interposed therebetween with the Galileanocu- Int. Cl G02b 23/00 lar positioned between the objective means andits focal plane Field of Search 350/20, 37, and the Galilean objectivepositioned between the eyepiece 38, 42, 54, 194, 212; 356/( lnquired)and the focal plane of the objective means` l 5 f i A ,4 y 5 li g; f

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PATENTEU HAR30 1971 SHEET 2 UF 3 l 9 LL.

/NVlfNm/es ROBERT E; CURTISS maw-n.

FRANK F. RANDVJR. BY .454

Attorney DUAL Pownn rsLnscorn BACKGROUND OF THE INVENTION This inventionrelates generally to telescopes, and particularly to dual-powertelescopes.

i-leretofore, dual-power telescopes have typically been of thesplit-field type. Such scopes enable an object to be viewed under twodifferent powers of magnification simultaneously with a single eyepiece.The field of view, by which is means the angular expanse which may beseen through the telescope eyepiece, is divided into two parts. One partcontains the scene under relatively low magnification while the otherpart contains a smaller portion of the scene under higher magnification.Such scopes have found particular utility in weapon carriers such astanks and other armored vehicles. They are exemplified by U.S. Pat. Nos.2,388,673, 2,512,153 and 2,527,719.

In addition to the split-field type of dual-power telescopes there havealso heretofore existed scopes, such as that shown in U.S. Pat. No.3,064,526, through which a field of view may be seen by means of asingle eyepiece, one portion of which is magnified and another portionof which is not. Furthennore, as seen by reference to U.S. Pat.2,409,186, telescopes have also been devised in which a portion of amagnified field of view is magnified still further. It is thisparticular type of' dualpower telescopes with which the presentinvention is particularly concerned.

Dual-power telescopes of the type providing a magnified eld of' view, aportion of which is magnified to a greater power than the balance of thefield, provide observers distinct advantages over the use of twoindependent telescopes of different magnifications or the use of asingle telescope system having two independent eyepiecesthrough which afield of view may be seen under variant degrees of' magnification. Theysimilarly offer advantages over the use of a single telescope havinginterchangeable eyepieces capable of sequentially providing multipledegrees of magnification. The principal advantage here rests with theavoidance of reorientation in shifting magnifications which is madepossible when a portion of a magnified field of view is magnified to agreater extent than the bdance of' the field. With such a dual-powertelescope an oerver may use the less magnified field of view forscanning or finding purposes. An object found to be of particularinterest may then be observed in greater detail within that portion ofthe field under higher magnification without having to change eyepiecesor move ones head and in doing so risk losing ones sense of orientation.

The principal problems associated with the just-described teiescopes ofthe prior art have arisen from their complexity. The dualpower telescopesystem depicted in U.S. Pat. No. 2,409,186, for example, requires twoparallel casings and a number of mirrors and lenses spaced apart withinrelatively concise tolerance ranges. Here light within the highermagnified portion of the field of view traverses three lens systems andis reflected by four independent mirrors, The presence of these numerousoptical elements compounds many of the problems commonly associated withoptical systems such as those of spherical and chromatic aberration.Their cost and susceptibility to damage is also high.

Accordingly, it is the general object of the present invention toprovide an improved telescope.

More specifically, it is an object of the present invention to providean improved dual-power telescope in which two portions of a field ofview may be simultaneously observed, the magnification of each portiondiffering from that of the other portion.

Another object of the invention is the same as the preceding object inwhich the magnification of each portion of the field of view may bevaried.

Another object of the invention is to provide a dual-power telescopehaving two concentric, annular fields of view withthe inner field beingmagnified to a greater power than the outer field.

SUMMARY OF THE INVENTION Briefly described, the present invention is animproved telescope having objective means and an eyepiece spaciallyseparated along the telescope axis a distance greater than the focallength of the objective means. A Galilean telescope is disposedbetweenthe objective means and eyepiece with the *Galilean telescopeobjective spaced from the objective means a distance greater than saidfocal length and the Galilean telescope ocular spaced from the objectivemeans a distance less than said focal length.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a diagrammatical view incross section of a preferred embodiment of a telescope incorporatingprincipals of the present invention.

FIG. 2 is a schematic illustration of a preferred relative dispositionof certain optical elements of the telescope shown in FIG. 1.

FIG. 3 is a tracing of sample light rays through the optical elementsshown in the telescope of FIG. l.

FIG. 4 is an example of the appearance of a field of view which may beobserved through the eyepiece of the telescope shown in FIG. 1.

FIG. 5 is a fragmentary view in cross section of mounting means forcertain optical elements shown in FIG. l.

FIG. 6 is another fragmentary view in cross section of mounting meansfor certain optical elements shown in FIG. I.

FIG. 7 is an end view of a telescope incorporating principals of thepresent invention having means for removing one or more optical elementsfrom the field of view.

Flg. 8 is a fragmentary, profile view, partly in cross section, of yetanother mounting arrangement for one or more optical elements in atelescope capable of providing variable magnification of a portion ofthe field of view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in more detail tothe drawing, there is shown in FIG. I a telescope adapted forterrestrial viewing which embodies principles ofthe present invention.The telescope comprises an objective l and an eyepiece 2 coaxiallymounted along telescope axis 3 within telescope housing 4. The objectivechosen here is of the telephoto-type comprising a convergent frontelement 5 and a divergent rear element 6. A telephoto-type objective ispreferred for its capacity of providing a relatively high ratio ofmagnification to focal length and thus relatively high magnification fora telescope of given overall length. Such type an objective alsoprovides variable magnification powers, or course. Where desired, othertypes of objectives such as wide angle, achromatic or even thin Iensesmay be substituted for the telephoto-type objective. The eyepieceselected here is of the orthoscopic type comprising two spaced,convergent, achromatic lenses 7. Other type of eyepieces could, ofcourse, be substituted.

A Galilean telescope 3, comprising a convergent objective lens 9 and adivergent ocular i0, is coaxially mounted along telescope axis 3 betweenobjective l and eyepiece 2 within telescope housing 4. By the termGalilean telescope is meant the combination of divergent and convergentlens means spacially separated along a common optical axis. Objectivelens 9 and ocular i0 are preferably doublets. The maximum diameter ofthe Galileantelescope shown here is approximately one-third that offrontal element 5 of objective i althougi it could be substantiallylarger and still provide dualpower magnification in combination withobjective l and eyepiece 2. The diameter of ocular I is somewhat smallerthan objective lens 9.

Mounted between Galilean telescope 8 and eyepiece 2 is a zero-powererector system lll comprising two convergent lenses l2 which also arepreferably doublets. If desired, a reticle may be incorporated betweenthe eyepiece and erector system.

Galilean telescope 8 is positioned so as to have objective lens 9 andocular il@ straddle the focal plane of objective l. Preferably, ocular110 is positioned with one of its focal plane located within theGalilean telescope approximately conjugate with the focal plane ofobjective ll. Objective lens 9 is preferably disposed a distanceapproximating the focal length of lens 9 less the other focal length ofthe ocular as measured outside the Galilean telescope along the opticalaxis thereof. With these relative dispositions light rays which passthrough both the telescope comprising objective I and eyepiece 2 andGalilean telescope 8, and light rays which pass through the telescopewithout traversing the Galilean telescope, are both focused upon acommon focal plane accessible for eye viewing, lt should be understoodhowever that neither ocular lll nor objective lens 9 neednecessarilyoccupy these precise positions provided they straddle thefocal plane of objective I. indeed, objective lens 9 may be mounted forrelative movement with respect to ocular l0 along their optical axisbeyond the focal plane of objective l by such means as will hereinafterbe described. Such adaptation permits variations to be made in themagnification of the image observed through the Galilean telescope inzoom fashion without defocusing.

The just described and preferred relative positions of objective l andthe elements of Galilean telescope 8 are shown in greater detail in FIG.2 in which line a represents the principal plane of objective l locatedclosest to the Galilean telescope, lines b and c represent the two focalplanes of ocular if), lines d and e represent two principal planes ofocular l0, and line g represents the principal plane of objective lens 9located closer to ocular lll. In addition to representing a focal planeof ocular llt), line c also represents a focal plane of objective l.Similarly, line c, in addition to representing another focal plane ofocular if), also represents a focal plane of objective means 9. Arrows htraversing objective means 9 denote the fact that the objective meansmay occupy various positions to the right of line c.

FlG. 3 illustrates several ray tracings through the telescope shown inFlG. l from which itis apparent that in passing through the telescopesome rays pass through the Galilean telescope while others do not. Thisis productive of' a field of view such as that diagrammatically shown inFlG. 4. Note here that two concentric portions of the field of view areunder two different powers of magnification. The magnification of theinner field, which actually is viewed through he Galilean telescope, ismagnified approximately 3 times the image of the outer field portionwhere the magnification provided by the Galilean telescope alone isthree. Thus the magnification of the inner field is the product of themagnification affordedby the Galilean telescope alone and themagnification provided by objective l in combination with eyepiece2.

With reference once again to FIG. 3, it will be confirmed that angle lcis some 3 times greater than angle l, and angle m some 9 times greaterthan angle n.

In FIG. l the inner and outer field portions are seen to be demarcatedby image ring I4 which is formed by the annular housing of Galileantelescope 8. The image of a thin vane l5 is also shown. This vane, whichmay be made of either metal or transparent material such as glass,provides support for the Galilean telescope. Vane l5 extends to housing4i where it may be mounted in various manners. FIG. 5 is illustrative ofa fixed mount in which screw i6 extends through hole i7 within housing land into shoe i8 which in turn is fixed to vane l5. Alternatively, vanel5 may extend to the exterior of the housing where it is manuallyaccessible and mechanically adapted for movement within the telescopehousing by means of an X-Y positioning drive mechanism. One suchmechanism is illustrated in FIG. 6 in which vane I5 passes through aslot in cylinder 2l, which cylinder is rotatably mounted within housing4. By manually moving knob 20, vane I5 may be moved in the plane of theFIG. either by sliding within the cylinder slot or by causing thecylinder itself to rotate.

FIG. 7 illustrates yet another mounting arrangement by means of whichthe Galilean telescope may be completely removed from the field of viewobservable through eyepiece 2. l-lere the Galilean telescope may beflipped in and out of housing t through a longitudinal slot therewithin.If desired, the slot may be bounded with magnetic material to hold theGalilean telescope in the withdrawn position illustrated by dashed linesin the FIG. For such adaptation a portion of vane l5 itself ispreferably metallic. A cover may also be placed about this outerposition to prevent dust and light from entering the slot.

FlG. 8 illustrates still another mounting arrangement which providesmeans for varying the magnification of the image seen through theGalilean telescope. Here vane I5 extends through slot 23 in housing 4.Collar 24 is fixed about the vane overlaying the edges of the slotthereby enabling an observer to slide the vane alongthe axis of thetelescope by means of knob 20. In the illustration objective lens 9 ismounted for movement along telescope axis 3. Obviously, it may beadapted by means of parallel bar guides to move along the optical axisof the Galilean telescope itself, parallel to axis 3.

Certain advantages offered by the described telescopes become readilyapparent from FIG. 4. The outer image here provides a relatively largefield of view for scanning. Once an object of interest has been found inthis relatively large field the telescope may be directed to the objectthereby placing it within the inner field where it may be observed underhigher magnification. Alternatively, the inner field may be moved offthe axis of the outer field without a repositioning of the telescope asa whole by means of the mechanism described in FIG. 6. The magnificationof the inner field or of both fields may then be increased. With neitherof these operations need the observer lose his orientation within thefield of view as might well be the case should one have to changeoculars or resight through an independent scope of higher magnification.Furthermore, from structural and optical viewpoints the telescopeprovides simultaneous dual-power viewing without the need for anymirrors and with relatively few optical elements of any nature. Inaddition, the image in both fields are sharply focused with a minimum ofspherical chromatic aberration.

It should be understood that the described embodiments are merelyillustrative of principles of the invention. Obviously, manymodifications may be made thereto without a departure from the spiritand scope of the invention as set forth in the following claims. Onesuch modification worthy of express note is that of eliminating thenegative lens element of the Galilean telescope entirely. `While thismodification is not preferred due to the resulting degradation in imagequality, it nevertheless is operatively feasible.

We claim: i

l. A dual power telescope for simultaneously viewing two superposedimages of the same object at different magnifications comprising anelongated housing, objective lens means, erector lens means and eyepiecelens means mounted in said housing in optical alignment along a commonoptical axis, said objective lens means forming an image of' the objectat the objective focal plane and the image being relayed by said erectorleas means to the focal plane of said eyepiece lens means, a Galileantelescope having a convergent objective lens and a divergent ocularlens, said Galilean telescope being positioned on said optical axisbetween said objective lens means and said erector lens means, with saiddivergent ocular lens facing said objective lens means and locatedbetween said objective lens means and said objective focal plane andwith said convergent objective lens facing said erector lens means andlocated housing and adjustably supporting said Galilean telescopelenses, and external adjusting means connected to said thin vane meansfor moving at least said convergent objective lens of said Galileantelescope along the optical axis.

1. A dual power telescope for simultaneously viewing two superposedimages of the same object at different magnifications comprising anelongated housing, objective lens means, erector lens means and eyepiecelens means mounted in said housing in optical alignment along a commonoptical axis, said objective lens means forming an image of the objectat the objective focal plane and the image being relayed by said erectorleas means to the focal plane of said eyepiece lens means, a Galileantelescope having a convergent objective lens and a divergent ocularlens, said Galilean telescope being positioned on said optical axisbetween said objective lens means and said erector lens means, with saiddivergent ocular lens facing said objective lens means and locatedbetween said objective lens means and said objective focal plane andwith said convergent objective lens facing said erector lens means andlocated between said erector lens means and said objective focal plane,the diameter of said Galilean telescope lenses being appreciably lessthan the diameters of said objective lens means and said erector lensmeans, and appreciably less than the diameter of the image formed at theobjective focal plane, thin vane means extending radially inward fromsaid elongated housing and adjustably supporting said Galilean telescopelenses, and external adjusting means connected to said thin vane meansfor moving at least said convergent objective lens of said Galileantelescope along the optical axis.